The subject of the present invention is a quick coupling for hydraulic fluid pipes. Such a quick coupling for hydraulic fluid pipes is known particularly from document EP-0 847 511 in the name of the Applicant.
Such a hydraulic coupling comprises, in a manner known per se, a male element and a female element whose ends which are to be connected are closed by valves, each valve comprising a shut-off member which comes into bearing contact with the shut-off member of the other valve upon connection, each shut-off member being pressed elastically against a seat in the open position of the coupling, the female element comprising an outer tubular part fastened to the end of a pipe or to a hydraulic receiver and inside which is slidably mounted a tubular coupling part for coupling the male part, which itself contains a valve, the tubular coupling part being slidably mounted in the outer part, in an insertion direction, against the action of elastic means, seals being provided between the two tubular parts and delimiting annular chambers, at least one of which is at the hydraulic pressure of the pipe or of the receiver to which the female element is fastened.
The problem which arises is that during the coupling phase, in the course of which the moving coupling part enters the outer tubular part, the pressure existing on the female part side, inside a pipe or inside the receiver, tends to oppose the connection.